Numerous medical procedures involve percutaneous insertions into a vein or artery. Among the more common are cardiac catheterization, intra-aortic balloon pumping (IABP) and percutaneous transluminal coronary angioplasty (PTCA). Each of these procedures typically begins with the placement of an angiographic needle through the skin and tissue of the patient's leg at a pulse point of the femoral artery immediately below the inguinal or groin crease. The needle is introduced until a spurt of arterial blood exits the needle hub, indicating that the tip of the needle has entered the femoral artery. A guidewire is then inserted through the needle and up through the femoral and iliac arteries into the aorta. The needle may then be removed, leaving the guidewire in place to serve as a guide for the insertion of an introducer sheath assembly or for the insertion of the intra-aortic balloon itself in the case of sheathless percutaneous procedures.
In order to ensure proper guidewire insertion, it is important that the angiographic needle enter the femoral artery at as shallow an angle as possible. Angles which are too shallow for a particular patient, however, may increase the distance between the artery and the patient's skin such that the needle is unable to reach and penetrate the artery, or may cause the needle to slide across the outside surface of the artery without entering it squarely. On the other hand, angles that are too steep may force the guidewire to make a sharp bend as it enters the artery. This sharp bend may create a kink in the guidewire, making it useless as a guide for the subsequent insertion of other devices. Hence, insertion of the needle at either too steep or too shallow an angle is unacceptable, and will require that the procedure be repeated in the contralateral leg. For patients of average weight, an entry angle of about 30.degree. is desirable. However, when a patient is obese, entry at an angle of about 30.degree. creates difficulties because of the extra thickness of the tissue overlying the artery. Therefore, obese patients often require entry at a more steep angle, with an entry angle of about 45.degree. being particularly desirable.
In addition to the importance of the angle at which the needle is inserted into the artery is the angle at which the needle is inserted relative to the axis of the patient's leg. If this angle is not correct, the needle may nick the artery rather than enter it squarely, again requiring that the procedure be repeated in the opposite leg.
As a result of these limitations on the orientation of the needle as it enters the femoral artery, positioning and orienting the needle by eye often results in insertion difficulties. There therefore exists a need for a device which will assure the insertion of an angiographic needle at the proper angle relative to the femoral artery and in the proper direction relative to the axis of the patient's leg so as to enable guidewires to be inserted into the artery without difficulty. Preferably, such a device will be inexpensive to manufacture so as to be disposable, and will accommodate needle insertions in patients of average weight, as well as in patients who are obese.